Rotational electric machines for vehicles, such as driving motors of hybrid electric vehicles and the like require acceleration performance such as startup, overtaking, and the like, and therefore, motors are required to have a high instantaneous peak torque. In a case of permanent magnet type rotational electric machines used for the purpose of automobiles, rare earth magnets having a high magnetic energy product are employed as permanent magnets used for the rotators generating this peak torque. In this case, dysprosium is added to the rare earth magnet used for the purpose of automobiles in order to withstand a high temperature environment. However, there is a high risk of resource depletion of the dysprosium, and therefore, application of rare earth-less magnets having less amounts of readily available permanent magnet materials, e.g., ferrite magnets and dysprosium, applied therein, is being reviewed from the perspective of avoiding risks.
In a case where a rare earth-less magnet is applied, the magnetic energy product is lower than the rare earth magnet, and therefore, it is necessary to pass a large electric current. For this reason, a high circuit loss occurs in a switching device of an inverter and a bus bar, and therefore, since it is necessary to take countermeasures to the heat, it is desired to reduce the electric current in the inverter when a peak torque is generated, i.e., it is desired to improve the torque characteristics of the motor.
As an example of a countermeasure, PTL 1 discloses a technique for changing the magnetic domain orientation of the permanent magnet in the circumferential direction to increase the effective magnetic flux, thus improving the torque, i.e., the efficiency.